#include <iostream>
using namespace std;


struct ListNode{
	int val;
	ListNode *next;
	ListNode(int x):val(x),next(NULL){}
};

ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode* heard=new ListNode(-1);
        ListNode* p=heard;
        while(l1!=NULL && l2!=NULL){
            if(l1->val<=l2->val){
                p->next=l1;
                l1=l1->next;
            }else{
                p->next=l2;
                l2=l2->next;
            }
            p=p->next;
           
        }
        p->next=l1==NULL?l2:l1;
       	return heard->next;
}
